Just recently my Blackberry has started lagging when I text an iPhone. After I send the text it will freeze on the message for about 30 seconds before returning to the message list. And also lags when I'm trying to open and read the message. It lasts for almost the whole day and happens about once a week. A few days ago I got a call while it was frozen on the message and my phone vibrated a bunch but nothing ever showed up and then finally when it went back to the messages it said I had a missed call.

Does anyone know what I should do about this?
Is it my phone or the iPhone?

Your phone does not communicate with any other phone directly; it gets routed through a carrier which manages any / all connections for you. Even PTT / PIN has some level of carrier or RIM integration.

it has nothin to do with the iphone part i have the same problem all the time it is becuz u are txting that iphone user alot correct? jsut clear out some of ur old messages n you should be find. im not sure but i think it has somthing to do wiht the phone goin therw all the old txt n opening only the last 7 (or how ever many u have it set to open)